Dual USB BGM-100s Mounted on Bench Grinder

[RickKrung]

Finally got around to setting up a new 8" Rikon low speed grinder with dual BGM-100 USB supports today.  I bought the grinder last May and the BGMs earlier than that, all before I had decided to get the diamond grinding wheels.  Recently, while using the coarse diamond wheel I was still wanting more aggressive and faster metal removal for creating basic bevels on seriously dull knives and repairs.  I dabbled with the 1x30" belt sander that I have but blew up a belt on a knife, separating the belt at the seam.

I'm doing knife sharpening at the Farmers Market in my tiny home town of Halfway, OR for the first time tomorrow.  It could be a tough crowd, cow-pokes and hunters, all of whom think they know how to sharpen things (many have said so when I have mentioned my sharpening activities).  So, maybe not related, but I was really wanting to have that more aggressive capability tomorrow, as I expect to see some seriously dull knives. 

So, with the belt sander not an option I want to trot out in public, I got serious today with the Rikon and BGMs.  I was a bit surprised at how easy it was, once I got into it. Turned out all I needed was a couple blocks of 4x4s for the BGM mounting supports, aligned them per the instructions and Viola!


I used the HanJig angle setting tool I made recently to set the grinding angle.  Worked quite well as the 8" grinding wheels are within the tool's envelope. 


My first usage was on a cheap Santoku 5" slicer that had a short section of unbeveled blade at the handle.  Not really a bolster, just an unground and unsharpened section.  I ground that to match the rest of the blade and put a nice clean 16º bevel on it.  I worked it until I got a burr along the entire edge.  I did notice the knife getting hot and at that "non-bolster" area, it turned color a bit, indicating it got too hot.  So, it will take some practice with a gentle touch to ensure the apexes don't get overheated, but I really like how it worked.  It has a better feel than the belt sander. 


I will be very happy taking that knife to any of my grindstones for final bevel grinding and honing/deburring.  The whole process will be much faster and with fewer grinding wheel changes.

Rick

[Ken S]

Rick,

Very interesting and informative post. Your cow-pokes and hunters share the all too common male idea that we somehow instinctively know how to sharpen. If so, why would Gillette have invented "the safety razor"? Why would the old barbers offer a "shave and a haircut"? Why would so many men in the pre Gillette era have worn beards? (I am in no position to criticize; I have had my present beard for twenty seven years.)

You have found a very workable set up. It should serve you well.

I have thought about converting my dry grinder with the BGM-100. I have the parts. I would be more likely to do it if my dry grinder was a lower speed eight inch model instead of a high speed six inch. Not having an eight inch dry grinder, and having an extra T4 Tormek, I explored the Norton 3X 46 and 80 grit wheel options. I did not try them with knives. Out of curiosity, did you try your 3X wheels with knives on your Tormek?

As I write this, you will be getting ready for your farmers market debut with your new set up. I wish you good success and am looking forward to reading your afterward thoughts. We are with you in spirit.

Ken

[RichColvin]

Rick,

I have a BGM-100 on one end of my 8" high speed grinder (a wire wheel on the other end).  I use it often when gross reshaping is needed. 

I usually keep an SVD-110 platform on it as it becomes a much better tool rest than I previously had.  Great for general purpose grinding (like taking the mushrooming off chisels after heavy use).

True, heat control is needed, but this is still a very viable part of my sharpening toolset. 

Kind regards,
Rich

[cbwx34]

....
...I did notice the knife getting hot and at that "non-bolster" area, it turned color a bit, indicating it got too hot. 
....

This is what ended my attempts at using a Bench Grinder on knives.  Even running the "cool" white wheels (which it looks like you're using too), on a slow speed grinder... the quick heat buildup amazed me.  Not always hot enough to "change the color"... but hot enough I couldn't touch it, even being careful and cooling the blade. (Way faster heat buildup vs. paper wheels, for example).  The most 'unforgiving' method I tried.

Good luck though... if anyone can do it... I believe you can!! 

[Jan]

Rick, I was wondering why you decided for dry grinding? From the point of view of knife sharpening your 8" Rikon is still a high speed grinder with some 1750 RPM. Without cooling it is very high risk that thin parts of edge will be overheated and loose its hardness.

Your nice set up may be used for drill bit reshaping or for gross reshaping far from the cutting edge. With care it may be also used for lawn mower blades sharpening. 

Jan

[Sharpco]

Rick.

I recommend CBN wheels for Rikon bench grinder because it generate low heat. And cool the blade with water at every 1 pass.

[RickKrung]

Thanks for the responses, all good ones. 

The Farmers Market in Haflway went very well today, better than any of the three I've done in Baker City.  My presence was advertised this week in two ways, one a "Halfway" Facebook page and I think the Farmers Market Facebook page.  There were several people who brought knives and scissors.  I sharpened three knives and one scissors while at the market.  I brought nine knives and a machete home for sharpening.  There was a good bit of chatting going on, but I need to speed up my through-put when at the market.  I was using the DC and DF diamond wheels and leather wheel honing.  There were many who asked if I was going to be back at subsequent markets.  I can't next weekend, but others later on, perhaps.  The market manager had told me they have only produce vendors every week and only every third week do they have in non-produce vendors.  One or more customers asked for me to come back and the manager came by and asked me to return next week and the week after.  That was all good.  (BTW, no cow-pokes or hunters came by, although I saw some drive-by, but there were no bullets flying  ).

Some of the knives I brought home have and will take some more extensive work to get sharpened.  One set of three were the worst knives I've ever seen.  Carbon steel.  The edges were pitted and chipped and very dull.  I tried working one on the Rikon and found things happen fast and not always what was intended.  I'm going to give the Norton 3X grind stones Ken gave me another try.  I'll only be using the 80 grit as I screwed up somehow and got a non-stainless steel hub glued into the 46 grit stone. 

The Rikon/BGM setup works really well and my original intent was to use it for roughing badly damaged drill bits and larger tools like machetes and mower blades, as Jan suggested.  I am very glad to have it set up finally as I was waiting for it and for the diamond wheels to arrive before getting into what drills I have that need sharpening. 

Rick

[Jan]

Rick, congrats to your successful debut, I rejoice with you! 

The major advantage of your Rikon set up is guided shaping, the major drawback is high over heating risk.

Jan

[Sharpco]

The Rikon/BGM setup works really well and my original intent was to use it for roughing badly damaged drill bits and larger tools like machetes and mower blades, as Jan suggested.  I am very glad to have it set up finally as I was waiting for it and for the diamond wheels to arrive before getting into what drills I have that need sharpening. 

Rick,
Machete is long but universal support is short. Will you use two jigs?

[RickKrung]

...snip...
Machete is long but universal support is short. Will you use two jigs?

I was planning on using a platform.  The idea of using multiple jigs had occurred to me and I have three that could be used, I just haven't had time to try anything out. 

I have two or three machetes of my own to practice with before tackling the customer's.  I'm thinking the platform may be the better choice as it allows for dealing with the curved tip.  However, as I think, I have the Pin Pivot Collar so that could be used on a jig places at the curved tip.  And with two standard-collared jigs for the straight body, could work.  Worth checking out. 

Rick

[RickKrung]

...snip...
I have two or three machetes of my own to practice with before tackling the customer's.  I'm thinking the platform may be the better choice as it allows for dealing with the curved tip.  However, as I think, I have the Pin Pivot Collar so that could be used on a jig places at the curved tip.  And with two standard-collared jigs for the straight body, could work.  Worth checking out. 

Rick

I checked out using multiple knife jigs on a machete, but it was awkward trying to bring the next jig collar into play as the machete was moved along the USB.  I abandoned that quickly for the platform.

Platform worked very well on the Rikon/BGM setup, except with the long knife on the platform the handle hit the opposite grinding wheel making for having to angle the knife, so the edge did not cross the face of the grindstone perpendicular (or square).  I didn't like the irregular grind result.  It would be nice to get rid of the other wheel, but then, when going from coarse to the medium wheel, it would have to be put on and the coarse one taken off.  I didn't. 

I practiced with my own machete first and was able to get a nice bevel, taking out nicks, etc. 


For my machete, I put the SB stone on for refining the bevel and then honed it on the leather wheel.  Got an average BESS score of 339 but it push cut copy paper just fine.  I thought all was good and proceeded with the customer's machete.

I didn't like the way this one behaved on the Rikon/BGM and I noticed what appeared to be discoloration as the apex was reached if I didn't sweep fast enough.  I think that could be why it didn't behave as well as far as the grind pattern went, when I wasn't able to consistently sweep smoothly. 

For finishing, I used the DC and DF diamond wheels followed by leather wheel honing.  BESS were exceptionally high, 799-1200.  I figured there must still be a burr, so used it on the Sharp Pad.  600-1200.  But it did push cut copy paper, but not nearly as cleanly as the first one. 

I examined the apex under the 60X hand microscope.  I could see half-moon depressions that looked fresh, as in after deburring, meaning the test media was crushing the apex during testing.  I'd read about this on the BESS Exchange but had not experienced it.  It seems the apex is weak and/or the steel is soft. 

I can think of two reasons why the steel might be soft, one, it just is soft, the other is the temper was taken out by grinding on the "high speed" grinder.  If the latter, then why did the first machete hold up.  It was ground in the same manner, except possibly faster passes over the stone (but not by much). 

The customer's machete is orders of magnitude sharper than when received.  I don't know how well the edge will hold up.  I can say one thing, sharpening a machete is not a $5 per blade job.

Rick

[RickKrung]

...snip...
Out of curiosity, did you try your 3X wheels with knives on your Tormek?
...snip..

Yes Ken, I have used the 3x wheels with knives, but they still mean wheel changes.  I was looking for an alternative that avoids wheel changes for those heavier metal removal tasks. 

Following Jan's cautionary comment about using the "high speed" grinder and heat, I decided not to use the Rikon/BGM on customer's knives, at least for now.  I'm glad I did.  I had one set of nice Henckels and two sets of carbon steel knives to work on.  I didn't want to chance damaging the Henckels or the others and as it turns out, the high carbon knives probably would not have stood up to the heat. 

I didn't have to do any heavy grinding on the Henckels, they were in pretty good shape, just dull.  I used the the Norton 3X 80 grit wheel on the two remaining out of the three set and on all four of the last set of carbon steel knives.  They all came out under 200 BESS off of the leather honing wheel and were all improved from 40-80 points (lower) after stropping with the Sharp Pad, final scores 117-147. 

With completion of the machete today, all of the take-home work is done and I can turn my attention to getting ready for a yard sale next weekend. 

Rick

[Sharpco]

Nice even bevel 

[Ken S]

Rick,

You would need to do some test runs, however, I believe that coarser wheels, like the 3X, especially the 46 grit, run cooler than finer stones.

Ken

[Ken S]

This video has some good information about using a 46 grit 3X wheel and also the perils of cooling high speed steel at around 60 minute mark.

https://vimeo.com/277800845

Ken